1. Field of the Invention
The present invention relates to a multi chip module cooling apparatus and, more particularly, to a multi chip module cooling apparatus which can maximize cooling efficiency of a multi chip module and which is composed of simple constitution.
2. Description of the Prior Art
It is well known that construction of a high speed broadband asynchronous transfer mode (hereinafter referred to as "ATM") exchange network is economical for realization of a broadband integrated service digital network, and development of an ATM switching system is in progress. The ATM switching system is in the trend of high speed, large capacity, and miniaturization and high density of system according to the progress of semiconductor technology, material and parts technology and system packaging technology, and especially, the system packaging technology related to interconnection technology and cooling technology serves as the most important factor of deciding the performance of the system according to the increase of transmission speed of system to several hundreds Mbps (mega bit per second) to several tens Gbps (giga bit per second) due to the development of high speed device technology using a large scale integration (LSI) chip and a very large scale integration (VLSI) chip.
In a narrowband integrated service digital network using COB (card on board) method in which a card is mounted on a board, the heat flow rate value per unit area of chip module is no more than 0.01 to 0.1 W/cm.sup.2, therefore, a natural convection cooling method or low flow rate forced convection cooling method using air is used in cooling of system. However, the broadband integrated service digital network to realize picture transmission has information processing rate of several hundreds Gbps and uses a multi chip module other than a single chip module used in the narrowband integrated service digital network. The multi chip module can minimize signal propagation delay between chips due to high degree of circuit and can reduce dispersion of electromagnetic wave, thereby improving the performance of switching system. However, in case of using the multi chip module, the heat flow rate value per unit area is expected to be about 2 W/cm.sup.2.
That is, a plurality of LSI and VLSI chips are mounted in the multi chip module used to promote the high density, high integration and high speed of system, therefore, a lot of heat is produced in each chip at the time of operation of system. If the chips, which generate a lot of heat, are left in the system, the inside of the system becomes high temperature condition so as to be a cause of failure of parts. Also, such increase of generated heat increases the temperature of the inside of the system so as to delay the signal transmission time between the parts in the system, and incorrectly transmit the signal. Therefore, the reliability of the system is abruptly deteriorated, so that cooling apparatus different from conventional one is required.
Especially, since the heat flow rate value per unit area in the multi chip module used in global integrated services digital network which will use three dimensional mounting technology is expected to be more than 10 W/cm.sup.2, a cooling apparatus of high efficiency is needed.